ywxzm03 opened a new pull request, #960:
URL: https://github.com/apache/dubbo-go-pixiu/pull/960
**What this PR does**:
This PR optimizes consistent hash reuse in `EndpointSnapshot`.
For consistent-hash load balancers such as RingHashing and MaglevHashing,
when a new endpoint snapshot is published, if the new snapshot has the same
routing-relevant healthy endpoint set as the previous snapshot and the
consistent hash configuration is unchanged, the new snapshot reuses the
previously built `consistentHash`. This avoids unnecessary CPU work and memory
allocations caused by rebuilding the hash structure.
Main changes:
- Add safe cached consistent hash reuse logic to `EndpointSnapshot`.
- Reuse the previous hash only when the following fields are equivalent:
- load balancer policy
- consistent hash config
- healthy endpoint ID
- healthy endpoint address / host
- endpoint metadata
- Forbid reuse when endpoints are added or removed, endpoint addresses
change, the healthy endpoint set changes, the hash config changes, or metadata
changes.
- Add unit tests for reusable and non-reusable cases:
- Reuse is allowed when a health update does not change the healthy
endpoint set.
- Reuse is forbidden when a health update changes the healthy endpoint set.
- Reuse is forbidden when an endpoint address changes.
- Reuse is forbidden when an endpoint is added or deleted.
- Reuse is forbidden when the consistent hash config changes.
- Reuse is forbidden when endpoint metadata changes.
- Add benchmark coverage for snapshot refresh cost with unchanged healthy
sets for RingHashing and MaglevHashing.
**Which issue(s) this PR fixes**:
Fixes #942
**Special notes for your reviewer**:
This PR does not make any out-of-scope changes and keeps the following
constraints:
- Do not change consistent hash algorithms.
- Do not change endpoint identity generation.
- Do not reuse hashes based on slice pointer equality alone.
- Do not weaken health filtering.
- Keep lazy initialization behavior intact.
Verified with:
```bash
go test ./pkg/cluster/... ./pkg/server/... ./pkg/cluster/loadbalancer/...
go test -run '^$' -bench
'^BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet$' -benchmem
./pkg/server
```
Output:
Unit tests:
```text
ok github.com/apache/dubbo-go-pixiu/pkg/cluster (cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/healthcheck
(cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer
(cached)
?
github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer/internal/lbtest
[no test files]
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer/maglev
(cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer/rand
(cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer/ringhash
(cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer/roundrobin
(cached)
ok
github.com/apache/dubbo-go-pixiu/pkg/cluster/loadbalancer/weightrandom (cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/retry (cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/retry/countbased
(cached)
ok
github.com/apache/dubbo-go-pixiu/pkg/cluster/retry/exponentialbackoff (cached)
ok github.com/apache/dubbo-go-pixiu/pkg/cluster/retry/noretry
(cached)
ok github.com/apache/dubbo-go-pixiu/pkg/server (cached)
? github.com/apache/dubbo-go-pixiu/pkg/server/controls [no test
files]
? github.com/apache/dubbo-go-pixiu/pkg/server/controls/mocks [no
test files]
```
Benchmark:
```text
goos: darwin
goarch: arm64
pkg: github.com/apache/dubbo-go-pixiu/pkg/server
cpu: Apple M5
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=1/reuse-cached-previous-10
1607060 746.3 ns/op 1976 B/op 30
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=1/rebuild-uncached-previous-10
45808 26038 ns/op 20115 B/op 218
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=32/reuse-cached-previous-10
86304 13888 ns/op 23530 B/op 539
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=32/rebuild-uncached-previous-10
387 3078728 ns/op 380584 B/op 5749
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=256/reuse-cached-previous-10
10000 105583 ns/op 179754 B/op 4123
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=256/rebuild-uncached-previous-10
20 54802988 ns/op 1528823 B/op 45423
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=1024/reuse-cached-previous-10
2889 420657 ns/op 726992 B/op 16423
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/RingHashing/endpoints=1024/rebuild-uncached-previous-10
5 242039292 ns/op 4597780 B/op 181381
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=1/reuse-cached-previous-10
1605380 749.8 ns/op 1976 B/op 30
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=1/rebuild-uncached-previous-10
377761 3165 ns/op 9100 B/op 41
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=32/reuse-cached-previous-10
86888 13777 ns/op 23529 B/op 539
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=32/rebuild-uncached-previous-10
4636 253168 ns/op 766625 B/op 708
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=256/reuse-cached-previous-10
13172 88850 ns/op 179687 B/op 4123
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=256/rebuild-uncached-previous-10
164 7211631 ns/op 42814169 B/op 5413
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=1024/reuse-cached-previous-10
2998 420360 ns/op 726738 B/op 16423
allocs/op
BenchmarkClusterConsistentHashSnapshotRefreshUnchangedHealthySet/MaglevHashing/endpoints=1024/rebuild-uncached-previous-10
7 161302827 ns/op 514595870 B/op 21554
allocs/op
PASS
ok github.com/apache/dubbo-go-pixiu/pkg/server 26.679s
```
```release-note
NONE
```
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